Propeller



c. H. HAVILI. ET AL PROPELLER Filed July 18,

6 Sheets-Sheet 2 July 23, 1935.

. A MEL I/I/I//l//I/l/l 420" Filed July 18, 1933 6 Sheets-Sheet July 23,1935.

Filed VJuly 18, 1955 l PROPELLER 6 Sheets-Sheet 4- V lll.

Willi/I A July 23, 1935.

c. H. HAvlLl. E- r AL PROPELLER lFiled July 18, 1955 6 Sheets-Sheet 5 1|l 1 .Illllllblhlllllllllillrl July 23, 1935'.

c. H; HAVILI. ET AL PROPELLER Filed July 18, 1953 6 Sheets-Sheet 6Patented July 23, 1935 I l 2,008g

unirse Astares Parent eterea PROPELLEE?.

Clinton H. Havill and Albert S. Walton, East Orange, N. J., assignors toEclipse Aviation Corporation, East Orange, N. J., a corporationof NewJersey Application July 18, 1933, Serial No. 681,02li 20 Claims. (Cl.1470-162) This invention relates to propellers and more The above andother objects will be more particularly to propellers of the type havinga readily apparent from the following detailed plurality of blades, thelangularity or pitch of 4description when taken in connection with thewhich may be varied during operation. accompanying drawings. It is to beexpressly 5 In variable pitch vpropellers heretofore prounderstood,however, that the drawings are em- 5 posed and especially in instanceswhere the blade ployed for purposes of illustration only and are pitchof such propellers is automatically varied not designed as an expressionof the limits of the' during operation thereof, it has been founddesirinvention, reference being had to the appended able to provide somemeans for limiting the reclaims for this purpose.

duction in the pitch of the blades in order to In the drawings, whereinsimilar reference 10 avoid increases in engine speed above that fOrcharacters refer to similar parts throughout the which the engine wasdesignedE and at which sever-a1 views,

speed most eicivent operation thereof is obtained. Fig. i is a plan viewpartly in section of one One of the objects ofthe present invention isAform 0f the invention; i

to provide in a variable pitch propeller a novel Fig, 2 is a side viewpartly in section of the l5 construction whereby the pitch of the bladesmay parts shown in Figl 1;

be controlled in such a manner as to prevent the Fig, 3 is an axialsectional view taken on 1in@ speed of the engine driving the propellerfrom 3 3 of F1g 1'; A

increasing to a dangerously high value or a value Fig; 4 is aperspective view of the pitch limiting in excess of that speed at whichthe engine opercontrol mechanism embodied in Figs. 1 to 3; 20 ates mostefficiently. Fig. 5 is a view similar to Fig. 1 but illustrating Anotherobject of the invention is to provide in another form of the invention;

a propeller of the type wherein the pitch of the Fig. 6 is a side viewpartly in section of the parts blades is automatically varied, a novelmechashown in Fig. 5;

nism for limiting the reduction in the pitch of Fig. 7 is aplan viewpartly in section illustrat- 25 the blades after the pitch has beenreduced to a ing the pitch-limiting control mechanism empredeterminedminimum. ployed in Figs. 5 and 6, and l Another object is to provide avariable pitch Fig. 8 is a developed perspective view of certain ypropeller wherein the pitch of the blades is autoof the elementsconstituting such control mechmatically varied in accordance with thepropeller anism. 30

' thrust and which embodies a novel construction Referring moreparticularly to Figs. 1, 2 and 3,

operable to prevent a further decrease in the a variable pitch propellerembodying the principitch of the blades after the speed lof rotation ofples of the present invention is illustrated therein the propeller hasattained a predetermined'value. as being constituted by a rotatableengine shaft Still another object is to provide a propeller or extensionthereof I 0 and a hub II drivably 35 wherein the pitch of the blades isvaried in acconnected thereto, the latter being relatively cordance withthrust-responsive movement of the movable longitudinally of the shaft inresponse propeller hub relative to the driving shaft thereto the thrustexerted by the propeller blades and for and wherein acentrifugally-operable mech- -being provided with a plurality ofradially-ex- 4U anism cooperates with the hub toprevent further tendingsockets I2 and I3 adapted to rotatably 40 movement thereof in onedirection after a prereceive the inner or root ends of propeller bladesdetermined low pitch has been obtained. I 4. As will appear more fullyhereinafter, suit- A further object is to provide in a mechanism ablemeans are employed for rotating the blades of the type referred toabove, a novel means and i4 in their respective sockets to vary thepitch of shaft for limiting the change in pitch of the sive movement ofthe hubl relative to the shaft. blades in onedirection after the speedof the As shown, the propeller shaft I0 projects through propeller hasattained a predetermined value. a stationary member l5 Which may be, foreX- A still further object is to provide a novel ample. a DOIII. 0f theCrank CaSe 0f the engine variable pitch propeller construction embodyingadapted to'rotate the propeller. 50 relatively few parts, compactlyarranged and In order to e'ect a drivable connection between operable insuch a manner that the pitch of the the hub Il and the shaft i0, adriving member or blades willbe automatically varied to yield maxblockIG is splined to the shaft,vFigs. 1 and 3,- and imum propeller andengine efficiencies under subis preferably rigidly maintained thereonby' any stantially all operating conditions. suitable means, such as.for example, split front 55 method for employing the power of thepropeller said blades during the aforesaid thrust-respon- 45 and rearcones I1 and Iii` respectively, a nut I9 threadedly received by theouter end of shaft I0 and interlocked with the front cone I1 beingprovided for maintaining these parts in proper operative relation withrespect to the shaft. After assembly of the parts heretofore mentioned,the nut I9 is preferably locked to an outwardly-extending portion 20 ofthe driving block I6 by any suitable means, such as a pin 2l. The hub II is also provided with a centrally-disposed aperture or opening 22,Fig. 3, which is adapted to receive the driving block I6, and aplurality of rows of ball bearings 23 are interposed between the drivingblock and hub in order to permit relative longitudinal movement betweenthese two members in a substantially frictionless manner.

Means are provided for rotatably mounting the inner or root ends of theblades I4 within the sockets I2 and I 3, and preferably such means areconstituted in such a manner as to' permit employment of the type ofpropeller blades now in common use. As shown, such -means include alongitudinally split sleeve 24, the two parts thereof being firmlysecured around the root ends of the blades by means of a collar 25 andan outer ring 26 threadedly received by a portion of the sleeveprojecting from the hub sockets, the collar 25 being rmly pressed on thesleeve surrounding the blade root.k The exterior surface of the sleeveis preferably so formed as to provide an annular shoulder 21 adapted toform an inner seat for an annular row of ball thrust bearings 28, theouter seat of said bearings being carried by a thrust ring 29 threadedlyreceived by the outer ends of the hub sockets and serving to maintainthe propeller blades I4 securely therein. Preferably, there is alsoprovided a plurality of ball bearings 30 positioned within each socketat the inner end thereof between the hub II and a portion of t-he ring25, in order to decrease the resistance to rotation of each blade in itsrespective socket.

Means are provided for interconnecting the rotatable shaft and eachblade vin order to effect rotation of the latter in their respectivesockets to vary the pitch thereof during longitudinal or axial movementof the hub with respect tothe shaft, and preferably such means aresecured to the shaft rearwardly of the propeller hub. In the form of theinvention illustrated, such means are constituted by a lever or linkmechanism, Fig. 2 one end of which is operatively connected with thecollar 25, while the other end is secured to a lateral extension or arm3I formed integrally or otherwise secured to the driving member I 6.More particularly, the above link mechanism includes a stud 32 securedto the collar 25 and extending laterally of the propeller blade andthrough a suitable aperture 33 formed in the hub socket. A screw member34 is threadedly attached to the arm 3I and this last named member andthe stud 32 are pivotally connected as by means of ilink 35. From thisconstruction, it will be appreciated that since one end ofthe linkmechanisms is rigidly connected to the driving member I6 which is inturn rigidly secured to the propeller shaft I0, the said mechanisms willeffect a rotation of each respective blade about its longitudinal axis norder to vary the pitch during longitudinal thrust-responsive movementof the hub relative to the shaft.

In order to yieldingly oppose forwardA axial movement of the hub withrespect to the shaft for the purpose of arresting such movement atvarious positions along the shaft in accordance with the degree ofthrust exerted by the blades under the existing conditions, there ispreferably provided a plurality of resilient members, such as forexample, coil springs 36, arranged in a circle concentrically withrespect to the shaft and interposed between the hub II and a plate 31secured in any suitable manner to the portion 2| of the driving blockI6. It is desired to point out that the effect of springs 36 is to movethe hub II downwardly, as viewed in Fig. l, in order to increase thepitch of the blades, but as the hub moves upwardly, as viewed in thisgure, in response to the thrust ofthe blades, the springs 36 will becompressed and the pitch of the blades will be decreased by the linkmechanisms heretofore described, the construction being such that thesprings yieldingly oppose the thrust-responsive movement of the hub andserve to arrest the latter in such a position relative to the shaft thatthe pitch of the blades assumedwill be substantially proportional to thethrust thereof and will yield maximum propeller eiciency for theconditions of thrust imposed. A.

Means are provided by the present invention for predetermining the lowerpitch limit of the propeller blades and preferably such means are soconstituted as to predetermine the lower blade angle at a specifiedspeed of rotation of the propeller. As shown, Figs. 1 to 4, such meansare constituted by a movable disk clutch element 38 carried by andnormally rotating with a flange 39 formed integrally with the drivingblock I6. As shown in Fig.l 4, centrifugally-operable members 40,disposed on either side of the propeller hub and pivotally connected toa plate 4I formed integrally with the driving block I6 and extensions 3I, are provided for moving the clutch disk 38 into frictional engagementwith a stationary clutch disk 42 secured in any suitable manner to thestationary casing portion I5, it being readily apparent that when suchfrictional engagement occurs, the speed of rotation of the disk 38 willbe retarded relative to the propeller. Any suitable means such assprings 38EL are provided for insuring that the clutch element 38 isnormally out of frictional engagement with respect to the disk 42.provided with cam portions 4311 for effecting the abovedescribed'movernent of the clutch disk 38 and the parts are preferablyso designed that frictional engagement between said disks will occur ata predetermined speed of rotation of the propeller only, there beingprovided a spring 43 securing one endof each of the weighted members 4I)to the propeller hub in order to bias such members to inoperativeposition until such predetermined speed has been obtained.

As heretofore pointed out, when the disk 38 is moved into frictionalengagement with the disk 42; relative rotation between the rst said diskand the propeller is effected and such relative movement is utilized insuch a manner as to prevent further forward movement of the hub rela`tive to the propeller shaftvwhich would effect a further decrease in thepitch of the blades. To this end, the disk 38 is provided with aplurality of diametrically-opposed pins/44 which project Preferably, theWeighted members 40 are v through the slotted ends of links 45, theopposite hub Il in any suitable manner.I Preferably, the

. ear 49jhas a guide member 52 'secured thereto and provided with aIslot 53 for receiving and guiding members45 and 46 in their pivotalmovement about the screw 48 and for holding said members in properposition against centrifugal force stresses. above that since the lever46 is pivotally mounted on a member secured to the propeller shaft andis operatively connected with the clutch disk 38 which normallyrotateswith the propeller, that retardation of member 38 by the stationaryclutch disk 42 will serve to employ the power of the propeller shaft'for moving the said lever about its pivotal mounting.

In order to substantially neutralize or compensate the propeller ,fromthe effects of centrifugal torsion on the blades, the result of whichwould be to decrease the pitch of the blades while the propeller is inoperation, the collars 25 associated with the root ends of each bladeare counterweighted or enlarged at diametrically-opposed sides asindicated at 54. The effect of these counterweights, as will be moreparticularly pointed out hereinafter, is to substantially oppose oroffset the centrifugal torsion on each respective blade while thepropeller is rotating.

During operation, considering the shaft III to be rotating in acounterclockwise direction, as viewed from the front, the hub II andblades I4 rotatably carried thereby will be moved axially of the shaftand relative thereto in response tothe degree of thrust exerted by theblades, the -link mechanisms referred to above being effective u ndersuch conditions to rotate the blades about their longitudinal axes-tovary the pitch. The springs 36 interposed between the plate 31 rigidlycarried by the shaft, and the hub, will be effective during such.thrust-responsive movement of the hub to yieldably resist such movementand arrest the forward travel ofthe hub in such a position as to yield amaterially increased propeller eili-V ciency4 for the thrust exerted bythe blades under the given conditions. When, however, during operationof the propeller, the pitchhas been reduced to such-a value asto-substantially lighten the load on the engine, the speed of the latterwill increase, thus effecting an increase in the speed ofthe propeller.As soon as a ,propeller speed has been obtained which corresponds to thetension of springs 43 associated with the weightedv vmembers 40,`thesaid members 40 will move outl 'wardly in response to centrifugal force,Fig. 4,

to effect,'by means of cams 46, frictional engagement between the clutchIdisks 36 and 42. As soon as the former of these disks is retardedrelative to the propeller, it will, by means of pins 44, rotate levers46, 41 in a clockwise direction about their pivotal mountings 46, asviewed in Fig. 1', and thus exert a force upon the hub II through, studs6I tending to move the latter downwardly, as, viewed in Fig. 1, inopposition to the force of thrusttending to move the hub upwardly. Atthis particular speed, the pitch of blades vwill beapredetermined-minimum and the hub will have a tendency to remain in astate of equilibrium as respects the longitudinal movement with respectto the p peller shaft. In the vevent that the speed of r ion ofpropeller tends to vexceed the `above supposed, lthecentrifugally-operable members 46 will increase the V'pressure betweenclutch disks 36 and 42 'tend'- to produce a further oscillation of thelevers 46 about their pivotal'mountings, which in lturn tends to movethe hub II downwardly with a It will be readily apparent from thegreaterforce. Such an operation would tend to increase the pitch of theblades but since an increase in pitch would impose a greater load uponthe engine, the net result would be a decrease in the propeller speedwhich would balance the supposed speed increase. It is, therefore, seenthat the centrifugally-operable mechanism serves not only to limit thereductionin the pitch of the blades but also effects a governingfunction for the engine.

Referring more particularly to Fig. 2, as heretofore'pointed out,.duringoperation, centrifugal torsion on the blades will tend to reduce thepitch thereof, and as viewed in this figure, will tend to rotate theblade I4 in a clockwise direction, thus placing links 36 in compressionand moving the hub forwardly of the shaft I0, whereupon the pitch of theblades will be decreased. However, the effect of centrifugal force onthe weighted portions 64 ofl the collars 26 secured to the roots of eachblade is such as to cause the collars to tend to turn the bladesin acounterclockwise direction, thus counteracting the above referred tocentrifugal torsion.v It is to be pointed out, however, that in certaininstances it may be desirable to counteract only a portion of thetorsion of the blades, in which event links 32, due to the small amountof ltorsion existing, will always be ,in compression during operation ofthe propeller.

Another embodiment of (the invention is disclosed in Figs. l5, 6, 'I and8, the propeller in this embodiment being'similar to the one heretoforedescribed with the exception that a modified form ofcentrifugally-operable mechanism is provided for predetermining thelower pitch limit of the blades. As shown, Figs. 7 and 8, the clutchdevice in this form is of the centrifugallyoperated type, the samebeingl constituted by a plurality of clutch shoes. adapted to bedrivably connected with a drum 6I by means of projection 62 receivablein slots 63, the said drum beingrigidly secured, as by means of screws64, to a. cam member 66 rotatably carried byadepending ange 66 formedintegrally with the plate 4 I. A plurality of garter springs 61 receivedin grooves 63 formed in the clutch blocks are provided for normally'maintaining the said blocks in inoperative position, the tension ofsuch springs being such," however, that under the action of centrifugalforce thevclutch blocks will move outwardly and frictionally engage ahollow ary drum 63 secured`to the casing I6. It will be apparent fromthe above' that normally the-cam member 66, drum 6I'and clutch blocks 60all rotate'as a unit with the propeller but that after a predeterminedspeed of rotastationtion ofthe propeller has been obtained, due tounderstood from this construction that when thev cam member 66 'partakesof relative motion with respect tothe propeller hub, the cam surfaces 16will rotate relatively to the cam rollers 1I and will ltend to move thepins 12 downwardly,

as viewedin Fig. 8, to'thus arrest further thrustrfespoiisive movementof the h'ub tending to del crease pitch of y In order to eiilcientlywithstand the thrust of the cam member 65 against the driving block I6during operation of the said cam member, and to equalize the tension onthe diametricallyopposed pins 12, the said member is provided with aninternal ledge 13 having a pair of diametrically-opposed slots 14 formedtherein for reception of projections 15 formed integrally with a bearingrace 16 which latter cooperates with bearings 16a. Preferably, the endsof the slots 14 and the extremities of the projections 15 are slightlyrounded in order to form a two-point support for the cam member 65, itbeing apparent from this construction that the portions of the cams 10engaged by the cam rollers constitute in eilect equal arms of a leverwhose fulcrum includes the points of engagement between projections 15and slots 14. As shown in Fig. 5, the pitch of cams 10 is such thatthrust-responsive movement of the hub to decrease the pitch of theblades will not be prevented during normal operation of the propeller.

Preferably, means are provided for adjusting the tension of one .or moreof the garter springs 61 in -order to vary the speed at which the clutchblocks engage the drum 69 and hence in order to vary the lower pitchlimit of the blades. As shown, Fig. 8, adjacent ends of a pair of clutchblocks 60 are cutaway to form a recess 11* for receiving said adjustingmeans, the latter being constituted by a. shaft 11 rotatably mounted inthe drum 6|, the said shaft having a wheel 18 secured thereto in anysuitable manner. The ends of one of the garter springs 61 are secured todiametrically opposite portions of the wheel 18 and the tension of thisspring may be varied by rotating4 the said wheel through a notchedadjusting member 19 secured to the shaft and readily accessible throughan opening in the drum B9 normally closed by cover plate 8U. A springdetent 8| carried by the drum-6l is adapted to cooperate with thenotched periphery of the adjusting member 19 in order to maintain thelatter in a predetermined position after adjustment of the tension ofthe spring.

It will thus be appreciated from the foregoing description that thepresent invention provides a relatively simple but effective method ofpreventing the speedof the engine driving the propeller from increasingbeyond a predetermined value, which might otherwise occur if the pitchof the propeller blades were materially reduced. The construction alsoprevents the occurrence of this last named condition and thus enablesoD- eration of the engine and propeller at maximum eilicencies. Byutilizing the power of the propeller shaft for arresting movement of thepropeller hub and consequent further decrease in the pitch, it Will beapparent thata relatively light-weight and compactly arrangedcentrifugally-operable control mechanism may be employed, which is a.distinct advantage in aircraft instal- -lations wherein a light-weightconstruction is extremely desirable.

While two embodiments of the invention have been herein disclosed anddescribed, it is to be understood that the same is not limited thereto,but may be-'embodied in various forms without departing from the spiritthereof, as well understood by those skilled in the art. Reference will,therefore, be had to the appended claims for a definition of the limitsof the invention.

What is claimed is:

1. In a Variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in saidhub, means for automatically varying the pitch of said blades duringoperation of the propeller, and means separate from said pitch varyingmeans for limiting the change in pitch in one direction comprising amember normally rotating with said propeller and adapted to be retardedto rotate relative thereto. 2. In a. variable pitch propeller, arotatable shaft, a hub drivably connected therewith, a plurality ofblades rotatably mounted in said hub, means for automatically varyingthe pitch of said blades during operation of the propeller, a membernormally rotating with said propeller, and means for retarding themovement of said member relative to the propeller to-limit the reductionin pitch of the blades.

3. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plu- -rality of blades rotatably mounted in saidhub,

means for automatically varying the pitch of said blades duringoperation of the propeller, and means for limiting the reduction in thepitch of the blades at a predetermined speed of rotation of thepropeller including' armember normally rotating with said propeller, anda centrifugallyoperated device for retarding the rotation of said memberrelative to the, propeller.

4. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in the hub,the latter being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch of said bladesduring such thrust-responsive movement of the hub, and means forlimiting' the change of pitch in one direction comprising a memberrotating with said propeller but adapted to be retarded relativethereto;

5. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in thehub,vthe latter being movable longitudinally of said shaft in responseto the thrust of the blades, means operable to vary the pitch of saidblades during such thrust-responsive movement of the hub, a membernormally rotating with said propeller, and means for retarding saidmember to effect rotation thereof relative to the propeller for limitingthe reduction in the pitch of the blades.

6. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in the hub,the latter being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch of said bladesduring such thrust-responsive movement of the hub, and means for'limiting the reduction in the/pitch of the blades at a predeterminedspeed of rotation of the propeller including a member normally rotatingwith said propeller, and a centrifugallyoperated device for retardingsaid member to effect relative rotation thereof `with respect to saidpropeller.

7. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in the hub,the latter being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch of said bladesduring such thrust-responsive movement of the hub, and means forlimiting movement of the hub with respect to the shaft in a direction todecrease the pitch of the blades comprising a. member normally rotatingwith said propeller, and means operable in response to centrifugal forceat a predetermined speed of rotation of the propeller for effectingmovement of said member relative to the hub. l

8. In a variable pitch propeller of the type having a plurality ofblades the pitch of which vari'es automatically in accordance with thethrust thereof, centrifugally-operable means for substantiallyovercoming the torsion of the blades while the propeller is inoperation, and means for predetermining the lower pitch limit of theblades, said last named means including a member normally rotating withsaid propeller, centrifugally-responsive means operable at apredetermined speed of rotation for effecting relative movem-ent betweensaid member and the propeller and means for operatively associating saidmember and blades.

9. Ina variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plu-` rality of blades rotatably mounted inv thehub,

the latter being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch of said bladesduring such thrust-responsive movement of the hub, means operable bypower derived from said propeller while in operation for limitingmovement of the hub in a direction to decrease the pitch of the blades,and centrifugally-responsive means operable at a predetermined speed ofrotation 'of the propeller for Irendering said second means operable.

10. lIn a variable pitch' propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in the hub,the latr being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch of said bladesduring such thrust-responsive movementv of the hub, a member normallyrotating with said propeller, centrifugally-responsive means operable ata predetermined speed for retarding said member, and means forconnecting said member to said hub, whereby at said predetermined speed,further movement. of the hub in a direction to decrease the pitch of theblades will be prevented.

11. A propeller for aircraft comprising a plurality of blades, means forrotating said blades, means responsive yto the thrust of the blades andincluding a longitudinally-movable hub for changing the pitch of saidblades, and other means cooperating with said hub for predetermining thelower pitch angle of said blades, said other means lincluding a membernormally rotating with said propeller and connected withA said hub, andcentrifugally-responsive means for retarding said member to effectrelative movement between the latter and the propeller.

12. In a variable pitch propeller, -a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in thefhub,the latter being movable longitudinally of said shaft in response to thethrust of the blades, means operable to vary the pitch ofsaid bladesduring such thrust-responsive movement of the hub, a member normallyrotating with said propeller, a plurality of leverspivotally mountedwith respect to said shaft and connected with said member and hub, andmeans for retarding the movement of said member with respect to` thepropeller whereby said levers will preventfurther movement of the vh'ubin a direction to decrease the pitch of the blades. I

,13. In a variable pitch propeller, a rotatable shaft, a hubv drivablyv'connectedtherewith, a 18. In a variable pitch propeller having a shaft75 l plurality of blades rotatably mounted in the hub, the latter beingmovable longitudinallyof said shaft in response to the thrust oftheblades, means operable to vary the pitch of said blades during suchthrust-responsive movement of the hub, a member normally rotating withsaid propeller, a lever disposed on either side of the hub v andpivotally mounted with respect to said shaft, y said levers beingconnected with said member and hub, and means responsive to centrifugalforce for retarding the movement of said member relative to thepropeller whereby-.said levers will be moved about their pivotalmountings and will oppose further movement of the hub in a direction toreduce the pitch of the blades after a predetermined speed of rotationofthe propeller has beenattained.

14. In a variable pitch propeller having a plurality of blades, arotatable shaft, a hub movable longitudinally of said shaft, a drivingmember secured to said shaft and disposed between the latter and thehub, said member being provided with-a pair of laterally-extending armspositioned rearwardly of the hub, means connecting said arms and bladesto vary the lditch of the latter during movement of the hublongitudinally of the shaft, a clutch disk carried by said member andnormally rotating therewith, meansincluding a pair ofcentrifugally-responsive devicesoperable at a predetermined speed ofrotation of the propeller for retarding movement of said clutch disk,and means connecting said disk and saidhub and pivotallyconnected withsaid driving member for preventing further movement of the hub relativeto the shaftat said predetermined speed.

15. In a variablepitch propeller having a plurality of blades, arotatable shaft, a hub-movable longitudinally of said shaft, a drivingmember secured to said shaft and, disposed between the latter and thehub, said member being provided with a pair of laterally-extending armspositioned rearwardly of the hub, `means connecting said armsand -bladesto vary the pitch of the ,latterA during movement of the hublongitudinally of the shaft, a clutch disk carried by said member andnormally rotating therewith, a stationary member,centrifugally-responsive means for moving said disk into engagement withsaid stationary member for retarding rmovement ofthe disk to effectrelative rotation between thelatter and the propeller, and meansdependent upon lrelative rotation between the propeller and disk formoving the hub in one direction longitudinally of said shaft. I

16. In a variable pitch propeller, a rotatable shaft, a hubv drivablyconnected therewith, a plui 4blades during operation of the propeller, amember normally rotating with said propeller, and` means for retardingthe movement of saidv member relative to the propeller vto limit thereduc.- tion in pitch of the blades, said last named means including acentrifugayy-operated clutch mechanism. y

17. In a variable pitch propeller having a shaft l'and a plurality ofblades drivably connected thereto, means for automatically varying thepitch of the blades during operation of said shaft, means for utilizingthe power of said shaft when in,

operation for limiting the decrease in the pitch of the blades, andcentrifugally-operated means for controlling the operation of saidsecond named means. A

means for utilizing the power of said shaft when in operation forlimiting the decrease in the pitch of the blades, and acentrifugally-operated clutch mechanism rendering said second namedmeans operable at a predetermined speed of rotation of the propeller.

19. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted in saidhub, means for automatically varying the pitch of said blades duringoperation of the propeller, and

centrifugally-controlled power operated means separate from saidpitch-varying means for limiting the variation in pitch of said blades.

20. In a variable pitch propeller, a rotatable shaft, a hub drivablyconnected therewith, a plurality of blades rotatably mounted inv saidhub, means for automatically varying the pitch of said blades duringoperation of the propeller, and means separate from said pitch-varyingmeans and operated by power from said rotatable shaft at a predeterminedspeed for limiting the reduction in pitch of said blades.

CLINTON H. HAVILL. ALBERT S. WALTON.

